This project investigates the effect of glucocorticoids on the process of induced differentiation in neuroblastoma (using the C1300 murine model). Work on two aspects of this phenomenon is proposed. (A) The therapeutic effectiveness of glucocorticoids on tumors arising in A/J mice after inoculation of cultured neuroblastoma cells will be examined. Various dosages, schedules, and routes of administration of dexamethasone and similar steroids will be assessed by tumor incidence and latent period of tumor development. Tumors which develop will be profiled for DNA, RNA, protein and catecholamine contents. Results may indicate whether dexamethasone treatment would be useful in treatment of neuroblastoma. And (B) a demonstration and initial characterization of a cytoplasmic glucocorticoid receptor will be attempted using a competitive binding assay with 3H-dexamethasone as a radioligand. The affinity, saturability (and capacity), and specificity of a soluble protein complexing reversibly with glucocorticoids will be determined. This would serve a beginning towards investigating the mechanism of action by which glucocorticoids induce differentiation in murine neuroblastoma.